Rising Incidence of Renal Cell Cancer in the United StatesFREE

Author Affiliations: Division of Cancer Epidemiology and Genetics (Drs Chow, Devesa, and Fraumeni), and the Division of Cancer Control and Population Sciences (Dr Warren), National Cancer Institute, Bethesda, Md.

Design Calculation of age-adjusted incidence and mortality rates,
along with 5-year relative survival rates, using data from the National
Cancer Institute's Surveillance, Epidemiology, and End Results (SEER)
program.

Setting and Participants Patients diagnosed as having kidney
cancer from 1975 through 1995 in the 9 geographic areas covered by
tumor registries in the SEER program, which represent about 10% of the
US population.

Main Outcome Measures Incidence, mortality, and 5-year relative
survival rates by time periods.

Results The age-adjusted incidence rates for renal cell carcinoma
between 1975 and 1995 for white men, white women, black men, and black
women were 9.6, 4.4, 11.1, and 4.9 per 100,000 person-years,
respectively. The corresponding rates for renal pelvis cancer were 1.5,
0.7, 0.8, and 0.5 per 100,000 person-years. Renal cell cancer
incidence rates increased steadily between 1975 and 1995, by 2.3%
annually among white men, 3.1% among white women, 3.9% among black
men, and 4.3% among black women. Increases were greatest for localized
tumors but were also seen for more advanced and unstaged tumors. In
contrast, the incidence rates for renal pelvis cancer declined among
white men and remained stable among white women and blacks. Although
5-year relative survival rates for patients with renal cell cancer
improved among whites but not among blacks, kidney cancer mortality
rates increased in all race and sex groups.

Conclusions Increasing detection of presymptomatic tumors by
imaging procedures, such as ultrasonography, computed tomography, and
magnetic resonance imaging, does not fully explain the upward incidence
trends of renal cell carcinoma. Other factors may be contributing to
the rapidly increasing incidence of renal cell cancer in the United
States, particularly among blacks.

Figures in this Article

Malignant tumors of
the kidney account for more than 2% of cancer incidence and mortality
in the United States, with nearly 30,000 new cases and
12,000 deaths estimated for 1998.1 More than 80% of
kidney cancers arise in the renal parenchyma, with the remainder in the
renal pelvis.2 Nearly all kidney cancers originating in the
renal parenchyma are adenocarcinomas (renal cell carcinomas), whereas
the vast majority of renal pelvis cancers are transitional cell
carcinomas.

Recent clinical surveys have revealed that incidental detection of
renal cell carcinomas is rising, partly because of increased use of
imaging procedures, such as ultrasonography, computed tomography, and
magnetic resonance imaging (MRI).3- 5 This observation is
consistent with epidemiological data from the United States and other
countries suggesting that renal cell cancer may be on the
rise.2,6 To further clarify these trends, we examined the
incidence, mortality, and survival data from the National Cancer
Institute's Surveillance, Epidemiology, and End Results (SEER)
program. For comparison, we also analyzed trends for renal pelvis
cancer.

METHODS

Persons diagnosed as having kidney cancer from 1975 through 1995 were
identified from 9 population-based cancer registries in the SEER
program.7 The registries, accounting for approximately 10%
of the US population, are located in the states of Connecticut, Hawaii,
Iowa, New Mexico, and Utah, as well as the San Francisco–Oakland,
Calif, Seattle–Puget Sound, Wash, Detroit, Mich, and Atlanta, Ga,
metropolitan areas.

The study included microscopically confirmed cases of invasive cancers
of the kidney parenchyma or kidney, not otherwise specified
(International Classification of Diseases for Oncology, Second
Edition8 [ICDO-2] site code C64.9) and
renal pelvis (ICDO-2 site code C65.9), excluding nonepithelial
tumors (ie, melanomas, sarcomas, and lymphomas). The proportion of
cases microscopically
confirmed was more than 90% and varied little
during the study period. Cases with racial origin other than black or
white were excluded because their numbers were too small for detailed
analysis.

For analysis, cancer cases with anatomical site coded as kidney, not
otherwise specified, and histological codes of transitional cell,
squamous cell, or other papillary carcinomas (ICDO-2
morphology codes 8050-8130) were recoded to renal pelvis cancer. The
cases were classified by age (in 5-year age groups up to >85 years),
sex, and race. Incidence rates were calculated by summing the number of
cases diagnosed during each 3-year period from 1975-1977 to 1993-1995,
dividing by the sum of the corresponding midyear population
estimates provided by SEER, and multiplying by 100,000 (ie, per
100,000 person-years). Rates were age-adjusted to the 1970 US
population using direct adjustment. Trends in incidence rates were
evaluated for the seven 3-year periods, along with annual US mortality
rates from 1975 to 1995. Figures were prepared by plotting the rates at
the midpoint of each 3-year interval on the x-axis and using a
logarithm scale for the y-axis so rates of change could be compared
visually.9

RESULTS

From 1975 to 1995, there were 31,105 invasive cancers of
the renal parenchyma and/or kidney, not otherwise specified, and 4985
cancers of the renal pelvis diagnosed among whites and blacks in the 9
SEER study areas. During the study period, the age-adjusted incidence
rates for renal cell cancer among white men and women were lower than
those among black men and women, with rates of 9.6, 4.4, 11.1, and 4.9
per 100,000 person-years, respectively. The
corresponding rates per 100,000 person-years were 1.5, 0.7, 0.8,
and 0.5 for renal pelvis cancer, respectively. In contrast with renal
cell cancer, incidence rates for renal pelvis cancer were higher among
whites than blacks.

Renal cell cancer incidence rates increased between 1975-1977 and
1993-1995 by 2.3% annually among white men, 3.1% among white women,
3.9% among black men, and 4.3% among black women (Figure 1). Since the mid-1980s, the incidence
rates for blacks have surpassed those for whites in both sexes. The
increases in renal cell cancer incidence have occurred in all age
groups (data not shown). In contrast, the incidence rate for renal
pelvis cancer has declined slightly among white men and remained stable
among white women. The numbers of renal pelvis cancer among blacks were
too small for stable estimates of trends.

The greatest increase in renal cell cancer incidence rates occurred for
localized tumors, rising annually by 3.8% among white men, 4.7% among
white women, 5.0% among black men, and 5.6% among black women (Figure 2). However, rates for more
advanced tumors, including those with regional extension and distant
metastasis, as well as unstaged tumors, also showed increases in all
race and sex groups.

In addition, mortality rates for kidney cancer (subsite specification
unavailable) rose between 1975 and 1995 (Figure 3). The increases were more rapid among
blacks than whites, consistent with the upward incidence trends and the
lack of improvement in survival rates for renal cell cancer among
blacks (Table 1). In contrast, the
5-year relative survival rates for whites generally improved over time.
For renal pelvis cancer, the 5-year relative survival rate declined
slightly over time among whites, while the survival trend among blacks
was unstable due to small numbers.

COMMENT

It has been shown that incidental detection of renal cell
carcinoma has risen with increased use of imaging procedures, such as
ultrasonography, computed tomography, and MRI.3- 5 Based on
our analysis of unpublished data from the Health Care Financing
Administration, the use of abdominal or pelvic computed tomography
scans or MRI increased steadily from 2622 to 4536 per 100,000
Medicare beneficiaries between 1986 and 1994, a 73% rise during this
period. The incidence trends by tumor stage suggest an effect of early
detection because the increases in renal cell cancer were most
pronounced for localized tumors. However, upward trends were also
apparent for more advanced and unstaged tumors. This pattern, along
with an increase in the mortality rates for kidney cancer, suggests
that the detection of presymptomatic tumors
cannot fully explain the rising incidence of renal
cell carcinoma.

We considered the possibility that improvements in subsite
specification for kidney cancers may have contributed to the rising
incidence of renal cell cancer. This explanation seems unlikely because
renal pelvis cancer declined only among white men and the magnitude of
change could not have compensated for the increase in renal cell cancer
in all race and sex groups. Furthermore, tumor classification also was
based on histology, and microscopic confirmation surpassed 90% and
changed little over time.

Reasons for the racial disparity in incidence and mortality
trends, with more rapid increases among blacks than whites, are not
entirely clear. Obesity and hypertension are established risk factors
for renal cell cancer10- 12 and are more prevalent among
blacks than whites in the United States.13,14 However, the
upward trends in the prevalence of obesity have varied little among
race and sex groups.13 In addition, the prevalence of
hypertension has remained stable since the 1960s,14
although the number and variety of antihypertensive prescriptions
have risen steadily in recent decades.15,16 While
black-white differences exist in the incidence and prognosis of
hypertension and patterns and effectiveness of
therapy,17- 20 there are few data available by race on
trends in the use of diuretics and other antihypertensive drugs, which
has been related in some studies to the risk of renal cell
cancer.10 Smoking is also an established risk factor for
renal cell cancer, but the prevalence of smoking has declined since the
mid-1960s.21 However, given the long latency of tumor
development and the possibility of difference in smoking behavior for
those who have not quit, the upward smoking prevalence in earlier
decades might have contributed to the continuing increases in renal
cell cancer, particularly at older ages.

The declining incidence of renal pelvis cancer among white men and
relatively stable trends among white women and blacks may be explained
in part by the decreasing prevalence of 2 major risk factors, cigarette
smoking and the use of phenacetin-containing analgesics.10
The diverse incidence trends for renal pelvis and renal cell cancers
underscore the importance of distinguishing between these types of
tumors in future descriptive and analytical epidemiological studies.

In summary, the rapidly rising incidence of renal cell cancer in the
United States may be due in part to the increasing detection of
presymptomatic tumors, but a real increase is suggested by the upward
incidence trend for more advanced tumors and by a corresponding
increase in kidney cancer mortality. The increases in incidence and
mortality have been greater among blacks than whites, providing clues
for further research into the causes and prevention of these tumors.

Federation of American Societies for Experimental
Biology, Life Sciences Research Office. Third Report on Nutrition
Monitoring in the United States: Volume 1. Washington, DC:
Interagency Board for Nutrition Monitoring and Related Research;
1995:ES9-ES11.

Federation of American Societies for Experimental
Biology, Life Sciences Research Office. Third Report on Nutrition
Monitoring in the United States: Volume 1. Washington, DC:
Interagency Board for Nutrition Monitoring and Related Research;
1995:ES9-ES11.

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